linux-kernel - Re: [RESEND 2][PATCH v4] hexdump: fix for non-aligned buffers

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Date:	Thu, 9 Jul 2015 21:08:04 +0200
From:	"H. Mijail" <hmijail@...il.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	David Howells <dhowells@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jiri Kosina <trivial@...nel.org>, Joe Perches <joe@...ches.com>
Subject: Re: [RESEND 2][PATCH v4] hexdump: fix for non-aligned buffers


> On 09 Jul 2015, at 09:16, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> 
> On Thu, Jul 9, 2015 at 4:07 AM, Andrew Morton <akpm@...ux-foundation.org> wrote:
>>> The other alternative in Documentation/unaligned-memory-access.txt is the
>>> macro get_unaligned() from asm/unaligned.h. However, using get_unaligned()
>>> would mean a much more intrusive patch, since each case of the groupsize
>>> would be changed, and anyway we would still need to check
>>> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to avoid penalising everyone.
>> 
>> Actually, I think using get_unaligned() would be a better solution.
>> For architectures which have CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y,
>> get_unaligned() should be fast - just one instruction.

D’oh! You’re right, of course.

>> 
>> This way we avoid having different-appearing output on different
>> architectures.
> 
> Definitely.
> 
> A less optimal get_unaligned() will just be noise in the snprintf() processing
> time.
> 

OK, so thanks Andrew and Geert for your comments. I’ll reimplement using get_unaligned.

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